This invention relates, in general, to electronic devices, and more particularly, to materials and methods for providing temporary electrical contact.
Prior to shipping integrated circuit (IC) devices, semiconductor manufacturers generally screen the IC devices to ensure their reliability. Often, a burn-in testing process is used whereby a device is operated at a predetermined temperature level (typically at a fixed temperature in a range from about 85.degree. C. to about 150.degree. C.) over a prolonged period. Power is applied to certain contacts on the device during the burn-in period and performance is measured by monitoring output signals from the device. The burn-in process serves to screen out those devices that are susceptible to premature failure from, for example, latent defects.
Considerable interest exists in methods for performing wafer-level burn-in (WLBI) of IC devices to determine known good die per wafer before wafers are separated into individual devices. The attractiveness of WLBI over die-level burn-in techniques is due to its promise of simplicity, reliability, and low cost. One problem associated with WLBI is the lack of cost effective and reliable suitable for temporarily contacting a wafer to be tested to a test or probe substrate. One prior art method for WLBI includes using an anisotropically conductive rubber sheet sandwiched between a wafer to be tested and a probe substrate. One disadvantage with anisotropically conductive rubber sheets is the need to use a clamping device throughout the burn-in process to hold the wafer, the rubber sheet, and the probe substrate together to ensure good contact. Clamping devices are bulky and require frequent adjustment to avoid damaging the semiconductor wafer and/or the probe substrate. Additionally, because of their size, the clamping devices add significant thermal resistance and thermal mass thereby increasing burn-in process time. Furthermore, the clamping devices are not portable making it difficult to transport and store them (i.e., they are heavy and take up substantial space).
As is readily apparent, materials and methods are needed that simplify WLBI and overcome at least the above problems. It would be of further advantage to do so in a cost effective and reliable manner.